The Daily Beast's Andrew Sullivan blasted Republican presidential nominee Mitt Romney as a "brand new candidate" following this month's presidential debates, saying on the "This Week" roundtable that Romney "was like an alien that ripped off his mask" at the first debate.

"The big elephant in the room is that the Mitt Romney that showed up on October 3rd was like an alien that ripped off his mask and said, 'I'm brand new now,'" said Sullivan, editor of "The Dish" at The Daily Beast. "He has evolutionary ideology, like he still has evolving doctrines."

Sullivan, a self-identified conservative who supports President Obama and has criticized Romney regularly, called Romney a candidate who "has no core at all and has changed it a dozen times to appeal to whatever market share he's appealing to."

"I'm sorry, but Romney was a severe conservative from January to October, and now he's a new candidate," Sullivan said. "What I'm amazed at is why Republicans aren't scared about what he'll be in January or July."

Gwen Ifill, moderator and managing editor of PBS' "Washington Week" said that Romney's debate performances helped him close the enthusiasm gap that has long plagued him among Republicans.

"At this point in the campaign, all that matters is who's got the last-minute enthusiasm," Ifill said. "You cannot argue that the Republicans, who had gotten a little depressed, were enthused after what they saw in that debate… Ask people who won all three of those debates, they said that the president won the last two, Romney won the first one, but Romney won all three. That's how important that first one [was]."

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